Selection of the Bacillus thuringiensis Berliner strain to produce a parasporin with cytotoxic activity against MCF-7 breast cancer cells

Abstract

Bacillus thuringiensis (Bt) is a Gram-positive bacterium that is known worldwide for its entomopathogenic properties. Recent studies indicate that bacteria produces protein inclusions called parasporins (PSs) that have anti-cancer activity against several types of tumor cells. The present work aimed to select a Bt strain that produces an active PS against MCF-7 breast cancer cells, and to provide an initial quantification of its toxicity and protein concentration. Two batches of Bt strains were fermented, and the parasporins were produced and isolated. In vitro tests were performed in 96-well plates and analyzed by a spectrophotometer. Most peptides did not have any cytopathic effect, but the A14d2 strain produces a PS with high toxicity to cancer cells. In the MTT test, the A14d2 strain PS was efficient with an LD50 of 14.83μg/mL and a protein concentration of 520μg/mL. At the end of the experiments, this PS was added to bacterial cells that produce other biologically active bacterial toxins against MCF-7 cells, which allowed it to be produced by a safe and inert microorganism to humans. PSs represent a potential tool to treat this form of breast cancer by providing peptides that may be useful in therapy.